1. Field of the Invention
The present invention relates to an image forming apparatus which is used as a digital photocopier composed, for example, by connecting a laser beam printer and a scanner.
2. Description of the Related Art
In recent years, digital photocopiers (image forming apparatuses) have been in practical use which connect laser beam printers (image forming units), which form images by electronic photography methods, with image scanners (reader units), which read image information from original documents as image data by the movement of an optical carriage (scanning device). In this type of copier, that the forming of an image is only executed at the time of operation of the optical carriage in the scanning device in the forward direction. The reason for this was that, because synchronization with the laser beam printer was difficult, in the case of also trying to execute the forming of an image during the backward operation of the optical carriage, the sequence of reading the image data in the image sensor positioned in the optical carriage must be reversed, and also the positional control of the secondary scanning direction of the optical carriage must be accurately carried out. However, basically, laser beam printers themselves are designed to be able to perform image forming at high speeds (high-speed printing operation) provided image data is fed to them rapidly and continuously. At the same time, in scanners, there is the backward operation of the optical carriage which does not contribute to image forming. For this reason, it was not possible to increase the image forming speed in the printers above that which was required.
Since, as described above, in the conventional image forming apparatus, there was the backward operation of the optical carriage which did not contribute to image forming in the scanner, there was the disadvantage that the image forming speed in the printer could not be increased above that which was required.